The formed body comprising a calcium silicate as the principal component is called artificial wood or the like, and is widely utilized as a building material. As the manufacturing method, first, water is added to a siliceous raw material and a calcareous raw material to form a slurry mixture, and then gelated by reacting at about 900C. The gelated material is put in an autoclave, and allowed to react at 190.degree. to 250.degree. C. for several hours to synthesize xonotlite. Class fiber, surfactant, polymer dispersion and the like are optionally added to the xonotlite slurry in order to improve toughness, and mixed with stirring. Then, the slurry is poured in a mold form, and dehydrated by pressing. The pressed matter is dried at about 120.degree. C. to obtain a formed body (Cement and Concrete, No. 469, Mar. 1986, p 37-43).
Xonotlite is a calcium silicate hydrate, and CaO/SiO.sub.2 molar ratio is almost 1. The crystal system of xonotlite is, in general, pseudo rhombic lattice (a=17.17 .ANG., b=3.69 .ANG., c=6.96 .ANG., .beta.=89.6.degree.), and the composition formula is Ca.sub.6 (Si.sub.6 O.sub.17)(OH).sub.2. The crystal structure is characterized by having a fiber form of which the longitudinal direction extends along the b-axis. The, BET specific surface area of a xonotlite particle is about 25-30 m.sup.2 /g.
There are various patent applications with respect to calcium silicate formed body, and for example, Japanese Patent KOKAI No. 52-15516 discloses a method comprising mixing a siliceous raw material powder and a calcareous raw material powder in water and allowing to react under heating to obtain an aqueous slurry of calcium silicate, and adding a polymer emulsion thereto to be adsorbed by calcium silicate. Japanese Patent KOKAI No. 54-160428 discloses a method comprising adding hydraulic gypsum, a polymer emulsion and a coagulant for the polymer emulsion to calcium silicate produced from a calcareous raw material and a siliceous raw material through hydrothermal synthesis reaction to form an aqueous slurry, and forming followed by drying to obtain a formed body. Japanese Patent KOKAI No. 60-246251 discloses a method comprising adding a latex of styrene-butadiene copolymer containing carboxyl group and a cation type polymer coagulant to calcium silicate produced from a calcareous raw material and a siliceous raw material through hydrothermal synthetic reaction to form an aqueous slurry, and forming followed by drying to obtain a formed body. Japanese Patent KOKAI No. 63-85038 discloses a method comprising adding water to a mixture of a lime raw material and a silicate raw iiiiteriil to form a slurry, producing a slurry of calcium silicate crystals by heating with stirring in an autoclave, adding synthetic pulp or a thermally denatured one thereof to the slurry, dehydrating and forming followed by drying to obtain a formed body. Japanese Patent KOKAI No. 63-201050 discloses a method comprising mixing a lime stone raw material powder with a siliceous raw material powder, adding water thereto to produce a calcium silicate slurry through hydrothermal reaction, adding sepiolite which adsorbed a polymer emulsion and a reinforcing fiber to the slurry, dehydrating and forming by pressing, and drying to obtain a formed body. Furthermore, Japanese Patent KOKAI No. 63-260847 discloses Lliat in a method comprising adding a latex of styrene-butadiene copolymer containing carboxyl group to calcium silicate hydrate produced from a calcareous raw material and a siliceous raw material through hydrolliermal synthesis reaction to form an aqueous slurry and forniing followed by drying to obtain a formed body, the formed body is reinforced by a fibrous net body.
As mentioned heretofore, in every conventional calcium silicate formed body, calcium silicate such as xonotlile was produced from a calcareous raw material and a siliceous raw material through hydrothermal reaction by heating them at 190-250.degree. C. for several hours under a saturated water vapor pressure. The conventional calcium silicate formed bodies had a problem being expensive because of not only using a highly pure calcareous raw material and siliceous raw material as the raw materials but also consuming a great quantity of energy. Besides, the bending strength of conventional calcium silicate formed bodies was about 80-120 kgf/cm.sup.2, and the improvement in the strength was desired. Furthermore, the crystallization water per unit weight of xonotlite was small. Though the heat resistance is high, the xonotlite was poor in the autolysis to release the crystallization water which was also desired to be improved.